Primary production and limiting nutrients were studied by14C techniques in a small, shallow, subalpine lake. There was no relationship between productivity at any depth and light intensity at that depth. Samples taken near the lake bottom always had higher productivity than samples taken near the surface, probably due to more optimal nutrient conditions. Nutrient enrichment experiments support this hypothesis, since sediment extract and ethylenediamine-tetraacetic acid were always effective in enhancing productivity. The effects of other nutrients and nutrient combinations were less consistent, and tended to change through the summer. A large number of significant three, four and five factor interactions in midsummer indicated that the nutrient requirements of the algal community were most complex at this time. Although retention time increased through the summer from 10 to 71 hours, productivity tended to more closely parallel water temperature.